Well, I figured I'd come back here and close my thread here. The other cuttles didn't last more than a few weeks after the first one died. I knew it was coming, but it didn't make it any easier. All told, the oldest of them was about 8 months old. It was an amazing experience, and something to cross off the old bucket list. Not sure if I have it in me to do it again, at least not for awhile.
It feels like the cuttles are worse because you go through all the effort to raise these amazing little things from eggs, you feel sort of parental towards them? I don't know. I couldn't bring myself to come back here and write that closing post for several months.
I have had the same delay with octopuses, especially the "special" individuals who have interacted. Sy Montgomery captures the human-ceph connection very well in her Soul of an Octopus.
I am better about recording deaths within a day now though because I want to be able to go back and see how long each animal lived in captivity and I tend to forget dates if I don't record them. I also take and photograph final measurements - really, really hard to do but it requires action immediately after death.